How to Properly Measure for a New Door

Installing a new door might seem a little daunting, particularly if you’ve never done it before. By far the most important thing to think about however, is how to measure for it.

Let’s run through the process of measuring for a new door.

Steps To Measure

You want to measure the frame, rather than the door you’re replacing.

It might be tempting to measure the door you already have in place. After all, if that fits, then surely your new one will, too?

Unfortunately, it’s not quite that simple. Over its lifespan, an old timber door will warp and change shape. This is why it’s so much more 

Before you get started, you’ll need some materials:

• Tape Measure
• Spirit Level
• Pencil and notepad

If you’re going the extra mile then you can use:

• A laser measure
• Square ruler: To make sure the frame sits at a right angle

Step 1: Measure the height of a door

First, measure the height of the opening in three places: the left, right and middle of the door. 

This is to make sure that the frame hasn’t warped or moved.

These three measurements should be within ten millimetres of one another, or else the entire frame will need to be swapped out. You’ll want to use the shortest of these three lengths; that way you can be sure that the door will open and close properly.

When making these measurements, be sure to account for the height of the carpet, doormats or any other obstacles. That way you’ll be sure that the door can swing freely.

Step 2: Measuring the width of a door

Measure the width in three places: along the bottom, middle, and top of the frame.

Use the shortest of the three measurements to determine the maximum size of the door.

Step 3: Measuring the depth of a door

The final step in measuring a door opening is the depth of the door. 

Internal doors typically come in three different thicknesses, the most common of which is 35mm (although thicker insulating and fire doors might be 40mm or 44mm). 

Measure at various points along the interior of the frame to be sure of the side you need. 

Step 4: Check The Frame

Finally you’ll want to make sure that the frame is in good condition. 

Use a spirit level on the inside of the frame: the hinge side, the latch side, and the head side. If these are severely out of alignment, then the frame may need sanded down, or even replaced.